Chapter 3.1

Energy exists in different forms

Energy

All forms of energy cause changes to occur Wind causes flag to flutter Light bulb gets hot and glows You pick up a tennis racket, change position Hit tennis ball

The ability to cause a change Energy takes many different forms and has

many different effects.

Forms of Energy

Scientist classify energy into many forms pg 73

Mechanical Energy Sound Energy Chemical Energy Thermal Energy Electromagnetic Energy Nuclear Energy

Each form causes change in a different way.

Mechanical Energy

Energy that moves objects Example

Energy used to put a book on a shelf Energy used to turn a key

Sound Energy

Sound results from the vibration of particles in a solid, liquid or gas

Sound cannot travel through empty space

Chemical Energy

Energy that is stored in the chemical composition of matter

Amount of energy Depends on types of atoms Depends on arrangement of atoms

Examples When wood or gasoline burns chemical energy produces

heat Cells use chemical energy that our bodies store from the

food we eat

Thermal Energy

Total amount of energy from the movement of particles in matter Energy of the motion of atoms and molecules

Electromagnetic Energy

Energy transmitted through space in the form of electromagnetic waves

Can travel through empty space These waves include

Visible light X-rays Microwaves

Sun releases large amount that is absorbed by Earth

Nuclear Energy

The center of an atom, its nucleus, is the source of nuclear energy

When a heavy atoms nucleus breaks apart energy is released

When the nuclei of two small atoms join together energy is released

General Types of Energy

All forms of energy can be described in terms of two general types of energy Kinetic Energy – energy of motion

Increases as mass increases Increases as speed increases

Potential Energy – stored energy Due to position (pg 76)

Gravity, stretching, compressing chemical composition

Energy stored in food, fuel in rocket engine Potential and Kinetic Energy demonstration

Chapter 3.2

Energy can change forms but is never lost

Energy Changes Form

How does energy change form? Example – a match

PE is stored in the chemicals on the head of the match The flame releases that energy as light and heat

Conversions between PE and KE Examples – roller coaster, ski jumper, skate boarder

Using Energy Conversions Water stored behind a dam is changed to electrical

energy Pg 80 for other examples

Law of Conservation of Energy

States that energy can neither be created nor destroyed. It may appear that energy is lost or gained

It only changed form Example 2nd example Useful energy is always less than the total amount of

energy

Energy conversions may produce unwanted forms of energy Electrical energy may be converted into

unwanted sound energy – (ie) a fan

Energy Transfer Examples

Energy Efficiency

Measurement of usable energy after an energy conversion High efficiency

Converts greater percentage of energy into the desired form

Low efficiency Converts a greater percentage of energy into an

inefficient form